This invention relates to raster scan digital character displays.
In many computer system applications, such as word processing, accounting, and scientific applications, the need exists for display of data, both alphanumeric characters and graphics data. In known systems, the data is typically displayed using a raster scan format in which the characters are displayed on the face of a CRT on a line by line basis, with each character being formed from an m by n matrix of pixel elements, where m and n are integers; or the characters or graphic elements are formed using a bit mapped full screen display. The alphanumeric characters and the graphics elements are typically stored in a memory device as multibit digital characters which are read from memory and processed to provide the blanking signals for the CRT active elements. In many applications, the types of characters and graphic elements which can be displayed, i.e. the display data font, is restricted to the dedicated use for which the computer system is designed. In other systems, the font is limited severely by the size of the memory, so that only a relatively limited number of types of characters or graphic elements can be displayed. In still other systems, the resolution of the alphanumeric characters, and thus the quality of the display, represents a compromise between font size and the size of each individual character matrix.
In order to be suitable for a wide variety of potential uses, a computer system CRT display should possess both high resolution and large font size, as well as great flexibility in the choice of font types and special character types. In addition, such systems should also have the capability of displaying the information at a comfortable brightness and contrast level.